Plastic bag opening apparatus

ABSTRACT

A plastic bag opening apparatus is provided by which plastic bags stacked with pins being inserted into pin holes are smoothly opened and delivered one by one from the uppermost one of the plastic bags. The apparatus comprises a center holding member ( 13 ) pressing elongations ( 2 ) of bags ( 1 ) between two pin holes ( 3 ) and side holding members ( 14 ) pressing the elongations ( 2 ) on both outer sides of the pin holes ( 3 ). Pressing of the elongations ( 2 ) by the holding members ( 13 ), ( 14 ) is released by rotation of a rotating member ( 17 ), ( 37 ) around a rotating shaft ( 18 ), ( 38 ). When the elongations ( 2 ) are to be pressed, the rotating member ( 17 ), ( 37 ) is vertically positioned so that a pushing-up force acting on the elongations ( 2 ) is received by the rotating member ( 17 ), ( 37 ) in a dead point state in the vertical direction. A control device controls such that when the bag 1 is to be opened by being blown with air, the pressing by the side holding members ( 14 ) is released and when the bag 1 so opened is to be discharged, the side holding members ( 14 ) press the remainder of the stacked plastic bags 1 and the pressing by the center holding member ( 13 ) is released.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention generally relates to a plastic bag openingapparatus and more particularly to an apparatus for opening plastic bagsin a stack, one by one, where each of the bags has one edge of itsopening portion elongated, the edge so elongated is provided with twopin holes and a multiplicity of the bags are held together with pins,having upper ends free, being inserted into the pin holes.

2. Description of the Prior Art

In a packaging apparatus for making packages by filling articles inplastic bags for packaging purpose, it is necessary to open the bags,one by one, out of a multiplicity of the bags held together in a stack.In order to facilitate operation to open the bags, one by one, out ofthe stacked bags for packaging purpose, conventionally, it is so carriedout that, as shown in FIG. 8, a plastic bag 1 is formed having one edgeof its opening portion 0 elongated to form an elongation 2, theelongation 2 is provided with two pin holes 3, as shown in FIG. 9, andpins 04 are inserted into the pin holes 3 so that a multiplicity of thebags 1 are held together in a stack and the bags 1 in this state areopened, one by one, to be filled with articles.

When the bags held with the pins 04 being inserted into the pin holes 3,as shown in FIG. 9, are opened, one by one, to be used for packaging,each of the plastic bags 1 so opened must be released from the pins 04.Conventionally, it is so carried out that while the pins 04 are heldinserted in the pin holes 3, articles are filled in the plastic bag 1and by action of force acting following the packaging work or the like,the plastic bag 1 is torn off at the portion of the pin holes 3 forrelease from the pins 04. Numeral 05 designates a perforated lineprovided so that the plastic bag 1 can be easily torn off at the portionof the pin holes 3.

Nevertheless, at the portion of the pin holes 3 of the plastic bag 1 sotorn off, there remain broken fractions and the exterior appearance ofpackaged articles is damaged. Hence, in order to improve this problem,the applicant here has heretofore proposed plastic bag opening methodsby the Japanese laid-open patent applications 2000-255514 and2003-11920. In these methods, as shown in FIG. 10, pins 4 having upperends free are inserted into pin holes of a plastic bag 1 to holdtogether the plastic bags 1 in a stack, air is blown obliquely fromabove to partially open the plastic bag 1 and then an opening member isinserted into the bag to enlarge the opening of the bag. At the time ofso enlarging the opening, the plastic bag 1 is drawn out of the pins 4without being torn or broken.

In these new methods, it is necessary to always hold in a stable statean upper surface of the plastic bags 1 stacked with the pins 04 beinginserted into the pin holes 3. Especially, when the uppermost bag fullyopened is to be drawn out of the pins 04, the stack of the remainingplastic bags 1 is often deformed to thereby irregularly move the bags 1so that the bag opening operation is obstructed. In order to avoid theobstruction, it is necessary to accurately hold the stack of the bags sothat the bags 1 can be smoothly drawn out of the pins 04. For thispurpose, there is provided a holding member 5 so that the upper surfaceof the stacked bags 1 pushed up from below is always held at apredetermined level. That is, even if the stacked bags 1 are consumedone by one and the height of the stack is changed, the remaining bags 1are pushed up from below and the upper surface of the bags 1 is pressedto be accurately held at the predetermined level by the holding member5. What is now needed is an apparatus to securely operate the holdingmember 5 so that the upper surface of the stacked bags 1 pushed up frombelow is pressed to be held at the predetermined level as well as thepressing is released so that the bags 1 are discharged one by one fromthe uppermost one.

SUMMARY OF THE INVENTION

In order to satisfy the above-mentioned necessity, it is an object ofthe present invention to provide a bag opening apparatus constructed toopen plastic bags in a stack, one by one from the uppermost one, byblowing air obliquely from above toward the bags, where each of the bagshas one edge of opening portion elongated to form an elongation, theelongation is provided with two pin holes and the bags are held togetherwith pins, having upper ends free, being inserted into the pin holes. Inthe plastic bag opening apparatus so constructed, in order for theplastic bags to be smoothly opened and stably delivered, a pushing-upforce acting on the plastic bags from below is received to therebyalways hold an upper surface of the stacked plastic bags at apredetermined level as well as pressing of the stacked plastic bags andrelease thereof can be quickly and accurately carried out to therebysecurely open and deliver the plastic bags one by one.

That is, as a plastic bag opening apparatus that can achieve theabove-mentioned object, the present invention provides a plastic bagopening apparatus constructed to open plastic bags, where each of theplastic bags has one edge of its opening portion elongated to form anelongation, the elongation is provided with two pin holes and theplastic bags are held together in a stack with pins, having their upperends free, being inserted into the pin holes and opened one by one fromthe uppermost one of the plastic bags in the stack by being blown withair obliquely from above, characterized in that the plastic bag openingapparatus comprises a center holding member to press the elongationsbetween the two pin holes, side holding members to press the elongationson both outer sides of the pin holes and a control device to controlmovements of the center holding member and side holding members suchthat when the plastic bags are to be opened by the air blowing, thepressing by the side holding members is released and when the plasticbags so opened are to be discharged, the side holding members press theremainder of the plastic bags in the stack and the pressing by thecenter holding member is released and each of the center holding memberand side holding members is constructed such that the pressing of theelongations and release thereof are carried out by rotation of arotating lever around a rotating shaft and when the elongations are tobe pressed, the rotating lever is vertically positioned so that apushing-up force acting on the elongations is received by the rotatinglever in a dead point state in the vertical direction.

In the plastic bag opening apparatus according to the present invention,the elongation is formed by an edge of a lower sheet out of two sheetsforming the bag opening portion being elongated and while theelongations of the bags are held pressed by the center holding memberbetween the two pin holes, air is blown obliquely from above toward thebag opening portion. Thereby, the uppermost one of the bags heldtogether in the stack is partially opened and, at this time, the bag atthe portion of the pin holes is drawn out of the pins having their upperends free.

Then, an opening member that is vertically and/or horizontallyenlargeable is inserted into the bag opening portion so partially openedand the bag opening portion is enlarged to be fully opened. Thereby, theelongation, except the portion pressed by the center holding memberbetween the two pin holes, is lifted up so that the bag at the portionof the pin holes still inserted with the pins can be fully drawn out ofthe pins.

In this way, the bag opening portion is enlarged and the plastic bag atthe portion of the pin holes is drawn out of the pins without being tornoff or broken so that the plastic bag becomes ready for being filledwith articles. In the bag so opened, there remains no broken fraction inthe vicinity of the pin holes differently from the conventional case andpackaged articles having an excellent exterior appearance can beproduced. The remainder of the stacked plastic bags after the uppermostbag is so opened are pressed at the portion of the elongations by theside holding members on both outer sides of the pin holes. Hence, evenif the pressing by the center holding member is released for dischargeof the opened bag, the stacked plastic bags are pressed by the sideholding members and the stacked state of the bags can be stably held.

Also, in the plastic bag opening apparatus according to the presentinvention, the center holding member and side holding member arerespectively constructed such that the pushing-up force acting on theelongations from below is received by the rotating lever verticallypositioned so as to be in the dead point state in the verticaldirection. That is, the pushing-up force to push up the stacked plasticbags from below is securely received by the center holding member andside holding members and the upper surface of the stacked plastic bagscan be always held at the predetermined level. When the pressing of thestacked plastic bags is to be released, the rotating lever is onlyrotated around the rotating shaft and thereby the bag opening operationcan be smoothly carried out. Also, when the stacked plastic bags are tobe pressed, it is carried out by a simple structure that the rotatinglever vertically positioned becomes the dead point state in the verticaldirection to thereby securely receive the pushing-up force acting frombelow. Thus, even if the height of the stacked plastic bags changes orthe pushing-up force from below changes, the stacked plastic bags aresecurely held and the upper surface of the plastic bags can be alwaysheld at the predetermined level.

In this way, by the construction that at least one of the center holdingmember and side holding member always abuts on the upper surface of thestacked plastic bags, the stacked plastic bags pushed up from below aresecurely held so that the upper surface thereof is maintained at thepredetermined level. Thus, according to the plastic bag openingapparatus of the present invention, the plastic bags in the stack can bestably opened one by one from the uppermost one of the plastic bags.

In the plastic bag opening apparatus of the present invention asmentioned above, if the rotating shaft to rotate the rotating lever formoving the center holding member and side holding member is constructedto be rotated by elongation and contraction of an air cylinder, there isobtained a plastic bag opening apparatus in which a change-over betweena state where the rotating lever vertically positioned to be in the deadpoint state receives the pushing-up force acting from below and a statewhere the rotating lever rotated around the rotating shaft releases thepressing of the elongations of the bag opening portion can be easily,quickly and securely carried out.

Also, in the plastic bag opening apparatus of the present invention asmentioned above, if the pressing by the center holding member and sideholding member and release thereof are carried out by a constructionsuch that the rotating lever has its one end fitted with an engagingroller and a member having a slot with which the engaging roller engagesis moved by rotation of the rotating lever around the rotating shaft,there is obtained a plastic bag opening apparatus in which the centerholding member and side holding members are easily moved by rotation ofthe rotating lever so that the bag opening operation can be smoothlycarried out.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a plan view showing plastic bags set in a stack to be openedin a plastic bag opening apparatus according to the present invention.

FIG. 2 is an explanatory view showing a state that a bag openingoperation of the plastic bags shown in FIG. 1 is being carried out bythe plastic bag opening apparatus according to the present invention.

FIG. 3 is a view seen in the direction of arrow A of FIG. 2.

FIG. 4 is a side view showing a structure of a center holding memberused in the plastic bag opening apparatus according to the presentinvention, wherein the stacked plastic bags are pressed by the centerholding member.

FIG. 5 is the same side view of the center holding member of FIG. 4,wherein the pressing of the stacked plastic bags by the center holdingmember is released.

FIG. 6 is a side view showing a structure of a side holding member usedin the plastic bag opening apparatus according to the present invention,wherein the stacked plastic bags are pressed by the side holding member.

FIG. 7 is the same side view of the side holding member of FIG. 6,wherein the pressing of the stacked plastic bags by the side holdingmember is released.

FIG. 8 is a cross sectional side view of the plastic bag shown in FIG.1.

FIG. 9 is an explanatory perspective view showing a state that stackedplastic bags are held together by pins in a plastic bag openingapparatus in the prior art.

FIG. 10 is an explanatory side view showing a state that stacked plasticbags held together by pins having upper ends free are being opened in aplastic bag opening apparatus in the prior art.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Herebelow, the present invention will be concretely described based onan embodiment of a plastic bag opening apparatus according to thepresent invention with reference to FIGS. 1 to 3. In FIGS. 1 to 3,numeral 1 designates a plastic bag for packaging purpose that has itsthree sides except an opening portion 0 closed. One edge of a plasticsheet out of two plastic sheets forming the opening portion 0, that is,a lower side sheet in the figures, is elongated to form an elongation 2and the elongation 2 is provided with two pin holes 3 arranged with aninterval maintained between them.

A multiplicity of the plastic bags 1 so formed are held together in astack with two pins 4, having their upper ends free, being inserted intothe pin holes 3. The stacked plastic bags 1 are pressed by a centerholding member 13 at the portion of the elongations 2 between the twopin holes 3. Also, the elongations 2 of the stacked plastic bags 1 arepressed by side holding members 14 at peripheral portions of theelongations 2 on both outer sides of the two pin holes 3.

The stacked plastic bags 1 are pushed up from below with a predeterminedpressure by an air cylinder or the like and the construction is so madethat this pushing-up force is received by the center holding member 13and side holding members 14 to thereby always hold an upper surface ofthe stacked plastic bags 1 at the same level. In order for the stackedplastic bags 1 to be pushed up from below with the predeterminedpressure by an air cylinder or the like so that the same horizontalstate is always maintained regardless of the height of the stacked bags,an appropriate device of known constructions may be employed and oneexample thereof is shown in the Japanese laid-open patent application2002-20510.

After the plastic bags are held together in the stack, as mentionedabove, pressing by the side holding members 14 is released and air 7 isblown obliquely from above toward the opening portion 0 of the plasticbags from an air nozzle 6 so that the opening portion 0 of the uppermostbag is opened, as shown by solid lines 8 in FIG. 2.

The air 7 blown from the air nozzle 6 is a hot air of temperature of 50to 80° C. so that temperature of the bag 1 that is being opened isincreased and flexibility thereof is enhanced. Thereby, when articlesare to be filled in the bag 1, the bag is prevented from being broken bycorner portions or the like of the articles, which is preferable,although not essential. The concrete temperature of the air 7 can beappropriately selected in consideration of a material and thickness ofthe bag to be used, shape and stiffness of the articles to be filled,etc.

Then, an opening member 9 is inserted into the opening so formed by theair 7 from the air nozzle 6. The opening member 9 comprises four bars,that is, two lower bars 10 and two upper bars 11. Intervals between thelower bars 10 and upper bars 11, between the two lower bars 10 andbetween the two upper bars 11 are changeable by vertical and horizontalmovements of the bars.

After the opening member 9 is inserted into the opening of the bag 1,the upper bars 1 1 are moved upward so that the opening of the bag 1 isenlarged, as shown by two dotted chain lines 12. As the result of thebag partial opening action by the air 7 and/or the opening enlargingaction by the opening member 9, the bag 1 at the portion of the pinholes 3 is drawn out of the pins 4, having their upper ends free, thathave been inserted into the pin holes 3. At this time, the elongation 2is by no means broken or torn at the portion of the pin holes 3.

In this way, even if the pressing by the side holding members 14 isreleased, the pushing-up force of the stacked plastic bags 1 acting frombelow is received by the center holding member 13 so that the uppersurface of the plastic bags 1 can be always maintained at the samelevel.

After the uppermost bag 1 is drawn out of the pins 4 at the portion ofthe pin holes 3, the remaining stacked plastic bags 1 are held togetherby the side holding members 14, as shown in FIG. 3.

Next, construction of the center holding member 13 and side holdingmembers 14 will be described with reference to FIGS. 4 to 7.

As shown in FIGS. 4 and 5, the center holding member 13 is pivotablyfitted around a pivotal shaft 15 and is provided with a slot 16. Numeral17 designates a rotating member, constituting a rotating lever of thepresent invention, that is rotatably fitted around a rotating shaft 18.An engaging roller 19 is rotatably fitted to the rotating member 17 andis fitted in the slot 16 of the center holding member 13 to be rollablymoved along the slot 16.

The rotating shaft 18 to which the rotating member 17 is rotatablyfitted is provided with a lever 20 and the lever 20 is pivotably fittedto an upper end of a piston rod 22 of an air cylinder 21.

By this construction, when a piston of the air cylinder 21 is elongated,the rotating shaft 18 is rotated via the lever 20, the rotating member17 is rotated around an axis of the rotating shaft 18, the engagingroller 19 is moved along the slot 16 and the center holding member 13 ispivotally rotated around the pivotal shaft 15 in the clockwise directionin FIGS. 4 and 5. That is, a press state shown in FIG. 4 where thecenter holding member 13 presses the plastic bags 1 stacked with thepins 4 being inserted in the pin holes 3 is changed to a release stateshown in FIG. 5 where the pressing by the center holding member 13 isreleased by the center holding member 13 being so clockwise rotated.

On the other hand, while the center holding member 13 is in the statepressing the stacked plastic bags 1, as shown in FIG. 4, a lineconnecting axes of the engaging roller 19 and rotating shaft 18 of therotating member 17 is maintained vertical. Hence, even if a downwardpressing force acts on the engaging roller 19 from the center holdingmember 13, this force only acts on the rotating shaft 18 right belowthereof via the vertical rotating member 17 and by no means becomes aforce to rotate the rotating member 17. That is, the rotating member 17is in a dead point state. It is to be noted that in FIGS. 4 and 5,numeral 23 designates an air cylinder that always pushes up the stackedplastic bags 1. The pushing-up force of the air cylinder 23 is receivedby the center holding member 13 so that the upper surface of the stackedplastic bags 1 can be held at the same level.

Next, construction of the side holding member 14 will be described withreference to FIGS. 6 and 7. In FIGS. 6 and 7, the side holding member 14is fitted with a lever 31 that downwardly elongates and the lever 31 isfitted with a sliding member 32 via a bolt 33. The sliding member 32 issupported being fitted movably up and down in a groove 34 of a strut 30.

The lever 31 has its lower end fitted with a receiving member 35 and thereceiving member 35 is provided with a slot 36 that horizontallyelongates. Numeral 37 designates a rotating member constituting arotating lever of the present invention. The rotating member 37 has itsupper end side fitted with a rotating shaft 38 that is connected to anair cylinder and its lever end side fitted rotatably with an engagingroller 39.

The engaging roller 39 fitted to the lower end of the rotating member 37is fitted in the slot 36 of the receiving member 35 and the constructionis so made that when the rotating member 37 is rotated around an axis ofthe rotating shaft 38, the receiving member 35 is moved up and down viathe engaging roller 39.

In a state shown in FIG. 6 where the side holding member 14 is in thestate pressing the stacked plastic bags 1, a line connecting axes of theengaging roller 39 and rotating shaft 38 of the rotating member 37 ismaintained vertical. Hence, even if an upward pressing force acts on theengaging roller 39 from the side holding member 14 via the receivingmember 35, this force only acts on the rotating shaft 38 right abovethereof via the vertical rotating member 37 and by no means becomes aforce to rotate the rotating member 37 that is in a dead point state. Itis to be noted that in FIGS. 6 and 7, numeral 40 designates an aircylinder that always pushes up the stacked plastic bags 1. Thepushing-up force of the air cylinder 40 is received by the centerholding member 13 and side holding member 14 so that the upper surfaceof the stacked plastic bags 1 can be held at the same level.

In FIG. 6, when the rotating member 37 is rotated in the clockwisedirection around the axis of the rotating shaft 38, the receiving member35 is upwardly moved and the side holding member 14 is also upwardlymoved so that the pressing force acting on the stacked plastic bags 1from the side holding member 14 is released, as shown in FIG. 7.

It is to be noted that as in the case of the rotating member 17 withrespect to the center holding member 13, the rotating member 37 isrotated around the axis of the rotating shaft 38 by the rotating shaft38 being rotated by an appropriate air cylinder (not shown).

Now returning to FIG. 3, when the bag 1 is opened to the maximum size bythe interval between the lower bars 10 and upper bars 11 being enlarged,as mentioned above, articles to be packaged are inserted into the bag 1to be filled therein. It is to be noted that at an appropriate timebefore filling the articles in the bag 1, during the filling timethereof or after the filling thereof, the bag pressing force by thecenter holding member 13 may be weakened so that the uppermost bag 1 soopened is released from the stacked state of the bags.

When the bag 1 filled with the articles is to be discharged, the edgeportion of the bag 1 is released from the center holding member 13. Evenif the bag pressing force by the center holding member 13 is released,the elongations 2 of the bags 1 stacked thereunder are pressed by theside holding members 14 on both outer sides of the pins 4 so that thestacked state of the bags 1 can be maintained in order. Also, thepushing-up force from below of the plastic bags 1 in the stacked stateis received by the side holding members 14 in the dead point state, asmentioned above, so that the upper surface of the plastic bags 1 can bemaintained at the predetermined level.

As for the opening member 9, the construction is made such that when theopening member 9 is inserted into the opening of the bag 1, it canenlarge the opening in the vertical direction, in the horizontaldirection or both in the vertical and horizontal directions and the sizethereof may be appropriately selected corresponding to the size, shapeor the like of the bag to be opened.

In the foregoing, while the present invention has been concretelydescribed based on the embodiment, as illustrated, the present inventionis not limited to the embodiment but, as a matter of course, may beadded with various modifications in the concrete structure andconstruction without departing from the scope of the claims of thepresent invention as appended herein.

For example, in the embodiment, while the construction of the openingmember 9 has been described to enlarge the opening of the bag 1 by theupper bars 11 being moved straightly upwardly, as shown in FIG. 3, inplace thereof, such a construction may be employed that four bars aremoved obliquely upwardly and obliquely downwardly with an oblique angleof 45°, respectively, so as to enlarge the opening of the bag 1. Thatis, an appropriate one of known constructions as the opening member ofthis kind can be employed.

Also, in the embodiment, the construction of the rotating members 17, 37as the rotating lever has been described such that the engaging rollers19, 39, fitted to the rotating members 17, 37, are fitted in the slots16, 36 so that when the rotating members 17, 37 are rotated, the centerholding member 13 and side holding members 14 are caused to press thestacked bags 1 or to release the pressing and when the line connectingthe rotating shafts 18, 38 and engaging rollers 19, 39 becomes vertical,the dead point state of the rotating members 17, 37 is formed. But, notbeing limited thereto, an appropriate construction, except theillustrated one, of the center holding member and side holding membermay be employed, if they are constructed such that when the rotatingmember is rotated around the rotating axis, the pressing of theelongations 2 of the bags 1 is released and when the elongations 2 ofthe bags 1 are to be pressed, the rotating member becomes vertical toform the dead point state so that the pushing-up force from below of theelongations 2 is received by the rotating member.

1. A plastic bag opening apparatus constructed to open plastic bags,where each of said plastic bags has one edge of its opening portionelongated to form an elongation, said elongation is provided with twopin holes and said plastic bags are held together in a stack with pins,having their upper ends free, being inserted into said pin holes andopened one by one from the uppermost one of said plastic bags in thestack by being blown with air obliquely from above, wherein said plasticbag opening apparatus comprises a center holding member to press saidelongations between said two pin holes, side holding members to presssaid elongations on both outer sides of said pin holes and a controldevice to control movements of said center holding member and sideholding members such that when said plastic bags are to be opened by theair blowing, the pressing by said side holding members is released andwhen said plastic bags so opened are to be discharged, said side holdingmembers press the remainder of said plastic bags in the stack and thepressing by said center holding member is released and each of saidcenter holding member and side holding members is constructed such thatthe pressing of said elongations and release thereof are carried out byrotation of a rotating lever around a rotating shaft and when saidelongations are to be pressed, said rotating lever is verticallypositioned so that a pushing-up force acting on said elongations isreceived by said rotating lever in a dead point state in the verticaldirection.
 2. A plastic bag opening apparatus as claimed in claim 1,wherein said rotating shaft to rotate said rotating lever for movingsaid center holding member and side holding member is constructed to berotated by elongation and contraction of an air cylinder.
 3. A plasticbag opening apparatus as claimed in claim 2, wherein the pressing bysaid center holding member and side holding member and release thereofare carried out by a construction such that said rotating lever has itsone end fitted with an engaging roller and a member having a slot withwhich said engaging roller engages is moved by rotation of said rotatinglever around said rotating shaft.